Airbag systems have been used for several years as one of the primary safety mechanisms in vehicles. While airbags are installed in vehicles for purpose of passenger safety, the deployment of airbags in itself has over the years raised safety concerns. In the past, an airbag that suddenly deploys can be fatal to small children, and injure adults who are too close the point of deployment. Several approaches have been attempted in order to control airbag deployment and avoid safety issues. Many past approaches focus on reducing the speed and amount of inflation for an airbag when a small passenger is in the target car seat, when the passenger is either too close to the airbag, or when the passenger is in a nonstandard position.
PCT/DE01/00500 describes a classification system where a video camera measures the head height of the front passenger-seat occupant. A pressure sensor on the floor detects the presence of feet. Feet & small head height lead to 5th percentile female (1.50 m height, 50 kg weight), while no feet & small head height lead to 5-8 year-old child classification.
In U.S. Pat. No. 5,983,147, a video camera is used to determine if the front right seat is empty, occupied by a Rear-Facing Infant Seat (RFIS), or occupied by a person. A range camera is used to estimate the weight of the occupant. The image processing involved the following steps: (1) histogram equalization to reduce variations caused by lighting changes, and (2) comparison of an image over a seat to a library of stored images that are applicable to a given situation (18 components used in an example). Comparison is done by correlation. A sample covariance matrix is used to weigh correlations. Occupant distance from the dashboard is measured by converting disparity maps from a stereo camera to depth maps. The occupant is found by comparing an empty-seat image to the actual image. Landmark points on the dashboard are also seen in the image, and landmark-to-occupant distances are measured. When some function of these distances is too small, airbag deployment is inhibited.
PCT/SE98/00867 describes a system that has a light ray emitted from a rotating gimbal at a reference point. The driver sits in the car, then rotates the gimbal until s/he sees the light. A mechanical encoder measures the orientation of the gimbal, and an infrared or ultrasound distance sensor measures the distance between gimbal and the driver's eyes. This gives eye coordinates in three-dimensions, and an ‘anthropometric model’ uses these to look up ‘passenger parameters.’ A variation of this scheme is to use math to infer the position of the driver's eyes from the orientation of the rearview mirror, and an infrared or ultrasound sensor.
In PCT/US98/07685 another occupant type and position detection system is described. A single camera mounted on either A-pillar sees both the driver- and passenger-side seats. The scene is lit by infrared (IR) light-emitting diode (LED). The image is rectified with a correction lens to make the image look as if it were taken from the side of the vehicle. Depth is determined by defocus. An occupancy grid is generated, and compared to “stored profiles” of images that would be obtained with an empty seat, a RFIS, a person. To allow for shape and size variations, a “size-invariant classification of reference features” must be used. Size-invariant classification is in general a very difficult task, and this application does not disclose how features are compared to stored profiles.
In U.S. Pat. No. 6,422,595 and U.S. Pat. No. 6,325,414, a system is described where seat occupant's position and velocity are obtained through use of various types of sensors. One IR transmitter and two IR receivers are located on the instrument panel. The transmitter rays reflect from windshield and reflect from the occupant to be received at the two receivers to estimate the occupant's position.
U.S. Pat. No. 6,412,813 describes a method and system for detecting a child seat. Three ultrasonic transducers are used for presence detection. One transducer is used for transmission while the other two are used for reception. Variation between the two receptions is used to determine the type of the occupant as well as the mounting position of a child seat if it is occupying the seat.
U.S. Pat. No. 6,302,438 describes an occupant detection system for controlling the activation of an air bag inflator that incorporates a transmitter/receiver subsystem and a ranging subsystem that respectively measure the distances from a point of reference to the upper seat back and to the region in front of the upper seat back. If a normally seated occupant is detected from the difference of the respective distances, then the air bag inflator is enabled.
PCT/US01/19206 describes a system where an occupant sensor incorporates a three dimensional imaging system that acquires a three dimensional image of an object. The image is segmented to remove unwanted portions and to identify a region-of-interest, and the content thereof is classified responsive to a plurality of three-dimensional features. A stereo system, a light system and a laser range sensor has been provided as the three-dimensional sensor.
Various non-imaging based systems were also proposed in various patents. PCT/US00/22033 describes a weight-sensor array based system. U.S. Pat. No. 6,327,221 proposes an ultrasound based solution. PCT/US99/31310 proposes an electric field sensor. PCT/US96/10645 proposes a reflective capacitive proximity sensor. PCT/US97/18418 describes a system with multiple sensors including a weight sensor, a child seat sensor, a crash sensor and a seat belt sensor.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced. Any modifications necessary to the Figures can be readily made by one skilled in the relevant art based on the detailed description provided herein.